Field of the Invention
FIG. 12 is a plan view showing a projector 560 of a three-panel (R, G, B) type in a projection display. Light emitted from a lamp 562a is reflected on a converging reflector 561, is emitted from a light source 562 after ultraviolet rays and infrared rays are removed therefrom through an UV/IR filter 563, and is incident on a dichroic mirror 551. The dichroic mirror 551 transmits red light (R) and reflects green light (G) and blue light (B). The red light obtained by the separation in the dichroic mirror 551 is sent to a liquid crystal display panel for red 553 on which a red image is to be displayed upon being reflected on a total reflection mirror 552. The red light passes through the liquid crystal display panel 553 after the amount of its transmission is changed in the liquid crystal display panel 553, and is then sent to a dichroic prism 554 serving as photosynthesis means.
On the other hand, the green light (G) and the blue light (B) which are reflected on the dichroic mirror 551 are sent to a dichroic mirror 555. The dichroic mirror 555 reflects the green color (G) and transmits the blue light (B). The green light obtained by the separation in the dichroic mirror 555 is sent to a liquid crystal display panel for green 556 on which a green image is to be displayed. The green light passes through the liquid crystal display panel 556 after the amount of its transmission is changed in the liquid crystal display panel 556, and is then sent to the dichroic prism 554.
The blue light passing through the dichroic mirror 555 is sent to a liquid crystal display panel for blue 559 on which a blue image is to be displayed upon being reflected on total reflection mirrors 557 and 558. The blue light passes through the liquid crystal display panel 559 after the amount of its transmission is changed in the liquid crystal display panel 559, and is then sent to the dichroic prism 554.
The red image light, the green image light and the blue image light which are incident on the dichroic prism 554 are synthesized, and light obtained by the synthesis is emitted as color image light (R, G, B). The emitted color image light is projected on a screen (not shown) through a projection lens 564.
In the projector 560 of such construction, the arrangement precision of optical members (the degree of coincidence of optical axes) is important in improving the image quality. Each of the optical members is mounted on a case 560a of the projector 560. However, an attempt to heighten the processing precision of a member mounting portion in the case 560a in order to increase the above-mentioned precision increases the fabrication cost of the projector 560, which is not realistic.
Means for focus adjustment are respectively provided for the liquid crystal display panels 553, 556, and 559, and means for CG adjustment (adjustment for matching pixels of the liquid crystal display panels 553 and 559 with pixels of the liquid crystal display panel for green 556) are further respectively provided for the liquid crystal display panels 553 and 559. Such adjustment means is constituted by means for fixing a plate member (not shown) for supporting each of the liquid crystal display panels to the member mounting portion at a base of the case 560a of the projector 560 and slightly inclining the plate member, so that the liquid crystal display panel can be inclined and shifted along its optical axis (focus adjustment), and can be moved in its surface (CG adjustment).
Since the dimensional precision of the member mounting portion in the case 560a is not too high, as described above, it takes long to make adjustment (particularly, focus adjustment), and fine adjustment is not easy. Further, the focus adjustment and the CG adjustment in the liquid crystal display panel cannot be made until the projector 560 is completed.
FIG. 13 is a diagram showing the schematic construction of an example of a conventional rear projection display. The rear projection display comprises a projector 602, a projection lens 603, a reflecting mirror 604, a reflecting mirror 605, a case 601 containing the optical members, and a transmission type diffusing screen 606. Image light from the projector 602 is reflected on the reflecting mirrors 604 and 605 after through the projection lens 603. The image light reflected on the reflecting mirror 605 is incident on the rear surface of the screen 606, and is diffused and emitted from the front surface of the screen 606, so that a viewer can view an image in a position on the front surface of the screen 606.
In order to make a screen of the conventional rear projection display large, the projection lens 603 having a high projection magnifying power must be used, or the distance of an optical path from the projector 602 to the screen 606 must be increased. In the present condition, however, there is a limit on the projection magnifying power of the projection lens 603. When the projection lens 603 having a high projection magnifying power is used, the depth of the case 601 is rather increased depending on the structure and the arrangement of the reflecting mirror, so that it is difficult to make the case 601 thin. When the distance of the optical path from the projector 602 to the screen 606 is increased, the depth of the case 601 is similarly increased, so that it is difficult to make the case 601 thin.